|
|
A162941
|
|
Number of reduced words of length n in Coxeter group on 7 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.
|
|
0
|
|
|
1, 7, 42, 252, 1491, 8820, 52185, 308700, 1826160, 10802925, 63906150, 378045675, 2236381350, 13229622000, 78261652875, 462967596000, 2738748634125, 16201445085000, 95841881782500, 566965863568125, 3353964722666250
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
COMMENTS
|
The initial terms coincide with those of A003949, although the two sequences are eventually different.
Computed with MAGMA using commands similar to those used to compute A154638.
|
|
LINKS
|
|
|
FORMULA
|
G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(15*t^4 - 5*t^3 - 5*t^2 - 5*t + 1)
|
|
MATHEMATICA
|
coxG[{4, 15, -5}] (* The coxG program is at A169452 *) (* or *) LinearRecurrence[ {5, 5, 5, -15}, {1, 7, 42, 252, 1491}, 30] (* Harvey P. Dale, Mar 13 2018 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|